Technical Field
The present invention relates to a method for determining if a wire guide roller for slicing wafers has to be replaced; more particularly, the present invention relates to a method for determining if the wire guide roller having a plurality of V-shaped grooves, each having a copper line thereon, arranged column-by-column on a periphery direction thereof is failed after slicing a plurality of wafers, based on an optical image technology.
Background Art
In semiconductor field, a wafer has to be sliced to obtain a very huge amount of chips. To perform such task in a high speed, a multiple wire saws slicing technology is generally employed. In this technology, a wire guide roller having a plurality of V-shaped grooves arranged in a periphery direction thereof is prepared, and on each of which a copper line is disposed for the slicing purpose. A tense controller is utilized for providing a stability and a tense strength of the copper line. For a given depth and width of the V-shaped groove, a thickness of the chip is determined. Such slicing technology includes the abrasive material absent and abrasive material involved manners. However, both the slicing technologies are invasive and additionally waste the chip material. In slicing, the copper line is brought to abrade periodically on the V-shaped groove. And, the copper line may tend to become unstable, resulting in that the V-shaped groove is damaged. This may cause the sliced chips to have a non-uniform thickness and surface. Conventionally, a determination regarding if the wire guide roller may still be used, i.e. if the copper line and the V-shaped groove is undertaken by checking up the thickness of the sliced chips. Another fashion is to analyze a 3-dimensional special information within the V-shaped groove by using a probe scan for a precise examination object. However, an online V-shaped groove examination usually involves an examination time limitation, and the above examination does not meet the irreverent requirement.
There have been a few effort aiming at copper line abrasion based on image analysis in the high speed wafer slicing field; however, analysis and evaluation of the abraded V-shaped groove are still absent. Presently, the available abrasion evaluation is undertaken by using a contact ellipsometer, but which is considered very slow in speed and costly in price. Some projection based equipment has been also developed for actual analysis, but its measurement range is restricted by the analysis. An optical interference tomography is a contact measurement, and thus not appropriate to the massive V-shaped groove measurement. Some optical fiber based V-shaped groove analyses have been seen, but they are shallowly related to the wafer slicing field.
In view of the above, it may be known that there has long been the issue of the improper high speed V-shaped groove examination technology for wafer slicing. Therefore, there is quite a need to provide a technical means to overcome this problem.